Conventional articles of footwear generally include two primary elements, an upper and a sole structure. The upper and the sole structure, at least in part, define a foot-receiving chamber that may be accessed by a user's foot through a foot-receiving opening. The sole structure is secured to a lower area of the upper, thereby being positioned between the upper and the ground.
In athletic footwear, for example, the sole structure may include a midsole and an outsole. The midsole often includes a polymer foam material that attenuates ground reaction forces to lessen stresses upon the foot and leg during walking, running, and other ambulatory activities. Additionally, the midsole may include fluid-filled chambers, plates, moderators, or other elements that further attenuate forces, enhance stability, or influence the motions of the foot. The outsole is secured to a lower surface of the midsole and provides a ground-engaging portion of the sole structure formed from a durable and wear-resistant material, such as rubber. The sole structure may also include a sockliner positioned within the void and proximal a lower surface of the foot to enhance footwear comfort.
A variety of material elements (e.g. textiles, polymer foam, polymer sheets, leather, synthetic leather) are conventionally utilized in manufacturing the upper. In athletic footwear, for example, the upper may have multiple layers that each includes a variety of joined material elements. As examples, the material elements may be selected to impart stretch-resistance, wear resistance, flexibility, air-permeability, compressibility, comfort, and moisture-wicking to different areas of the upper. In order to impart the different properties to different areas of the upper, material elements are often cut to desired shapes and then joined together, usually with stitching or adhesive bonding. Moreover, the material elements are often joined in layered configuration to impart multiple properties to the same areas.
As the number and type of material elements incorporated into the upper increases, the time and expense associated with transporting, stocking, cutting, and joining the material elements may also increase. Waste material from cutting and stitching processes also accumulates to a greater degree as the number and type of material elements incorporated into the upper increases. Moreover, uppers with a greater number of material elements may be more difficult to recycle than uppers formed from fewer types and number of material elements. Further, multiple pieces that are stitched together may cause a greater concentration of forces in certain areas. The stitch junctions may transfer stress at an uneven rate relative to other parts of the article of footwear which may cause failure or discomfort. Additional material and stitch joints may lead to discomfort when worn. By decreasing the number of material elements utilized in the upper, therefore, waste may be decreased while increasing the manufacturing efficiency, the comfort, performance, and the recyclability of the upper.